nixos: fix typos

 - Use `Cm` to mark literal string arguments, e.g. the `boot` command argument passed to `nixos-rebuild`.

 - Optional flags or arguments should be marked with `Op`. This includes optional repeating arguments.

 - Required flags or arguments should not be marked.

 - Mutually exclusive groups of arguments should be enclosed in curly brackets, preferrably created with `Bro`/`Brc` blocks.

 - Mutually exclusive groups of arguments should be enclosed in curly brackets, preferably created with `Bro`/`Brc` blocks.

When an argument is used in an example it should be marked up with `Ar` again to differentiate it from a constant. For example, a command with a `--host name` flag that calls ssh to retrieve the host's local time would signify this thusly:

```

...

.Ed

```

Contents of code blocks may be marked up further, e.g. if they refer to arguments that will be subsituted into them:

Contents of code blocks may be marked up further, e.g. if they refer to arguments that will be substituted into them:

```

.Bd -literal -offset indent

{

- A large number of packages have been converted to use the multiple outputs feature of Nix to greatly reduce the amount of required disk space, as mentioned above. This may require changes to any custom packages to make them build again; see the relevant chapter in the Nixpkgs manual for more information. (Additional caveat to packagers: some packaging conventions related to multiple-output packages [were changed](https://github.com/NixOS/nixpkgs/pull/14766) late (August 2016) in the release cycle and differ from the initial introduction of multiple outputs.)

- Previous versions of Nixpkgs had support for all versions of the LTS Haskell package set. That support has been dropped. The previously provided `haskell.packages.lts-x_y` package sets still exist in name to aviod breaking user code, but these package sets don't actually contain the versions mandated by the corresponding LTS release. Instead, our package set it loosely based on the latest available LTS release, i.e. LTS 7.x at the time of this writing. New releases of NixOS and Nixpkgs will drop those old names entirely. [The motivation for this change](https://nixos.org/nix-dev/2016-June/020585.html) has been discussed at length on the `nix-dev` mailing list and in [Github issue \#14897](https://github.com/NixOS/nixpkgs/issues/14897). Development strategies for Haskell hackers who want to rely on Nix and NixOS have been described in [another nix-dev article](https://nixos.org/nix-dev/2016-June/020642.html).

- Previous versions of Nixpkgs had support for all versions of the LTS Haskell package set. That support has been dropped. The previously provided `haskell.packages.lts-x_y` package sets still exist in name to avoid breaking user code, but these package sets don't actually contain the versions mandated by the corresponding LTS release. Instead, our package set it loosely based on the latest available LTS release, i.e. LTS 7.x at the time of this writing. New releases of NixOS and Nixpkgs will drop those old names entirely. [The motivation for this change](https://nixos.org/nix-dev/2016-June/020585.html) has been discussed at length on the `nix-dev` mailing list and in [Github issue \#14897](https://github.com/NixOS/nixpkgs/issues/14897). Development strategies for Haskell hackers who want to rely on Nix and NixOS have been described in [another nix-dev article](https://nixos.org/nix-dev/2016-June/020642.html).

- Shell aliases for systemd sub-commands [were dropped](https://github.com/NixOS/nixpkgs/pull/15598): `start`, `stop`, `restart`, `status`.

- `/var/empty` is now immutable. Activation script runs `chattr +i` to forbid any modifications inside the folder. See [ the pull request](https://github.com/NixOS/nixpkgs/pull/18365) for what bugs this caused.

- Gitlab's maintainance script `gitlab-runner` was removed and split up into the more clearer `gitlab-run` and `gitlab-rake` scripts, because `gitlab-runner` is a component of Gitlab CI.

- Gitlab's maintenance script `gitlab-runner` was removed and split up into the more clearer `gitlab-run` and `gitlab-rake` scripts, because `gitlab-runner` is a component of Gitlab CI.

- `services.xserver.libinput.accelProfile` default changed from `flat` to `adaptive`, as per [ official documentation](https://wayland.freedesktop.org/libinput/doc/latest/group__config.html#gad63796972347f318b180e322e35cee79).

  You can check that backups still work by running `systemctl start mysql-backup` then `systemctl status mysql-backup`.

- Templated systemd services e.g `container@name` are now handled currectly when switching to a new configuration, resulting in them being reloaded.

- Templated systemd services e.g `container@name` are now handled correctly when switching to a new configuration, resulting in them being reloaded.

- Steam: the `newStdcpp` parameter was removed and should not be needed anymore.

- The `openssh` package now includes Kerberos support by default; the `openssh_with_kerberos` package is now a deprecated alias. If you do not want Kerberos support, you can do `openssh.override { withKerberos = false; }`. Note, this also applies to the `openssh_hpn` package.

- `cc-wrapper` has been split in two; there is now also a `bintools-wrapper`. The most commonly used files in `nix-support` are now split between the two wrappers. Some commonly used ones, like `nix-support/dynamic-linker`, are duplicated for backwards compatability, even though they rightly belong only in `bintools-wrapper`. Other more obscure ones are just moved.

- `cc-wrapper` has been split in two; there is now also a `bintools-wrapper`. The most commonly used files in `nix-support` are now split between the two wrappers. Some commonly used ones, like `nix-support/dynamic-linker`, are duplicated for backwards compatibility, even though they rightly belong only in `bintools-wrapper`. Other more obscure ones are just moved.

- The propagation logic has been changed. The new logic, along with new types of dependencies that go with, is thoroughly documented in the "Specifying dependencies" section of the "Standard Environment" chapter of the nixpkgs manual. The old logic isn't but is easy to describe: dependencies were propagated as the same type of dependency no matter what. In practice, that means that many `propagatedNativeBuildInputs` should instead be `propagatedBuildInputs`. Thankfully, that was and is the least used type of dependency. Also, it means that some `propagatedBuildInputs` should instead be `depsTargetTargetPropagated`. Other types dependencies should be unaffected.

  The slurmctld now runs as user `slurm` instead of `root`. If you want to keep slurmctld running as `root`, set `services.slurm.user = root`.

  The options `services.slurm.nodeName` and `services.slurm.partitionName` are now sets of strings to correctly reflect that fact that each of these options can occour more than once in the configuration.

  The options `services.slurm.nodeName` and `services.slurm.partitionName` are now sets of strings to correctly reflect that fact that each of these options can occur more than once in the configuration.

- The `solr` package has been upgraded from 4.10.3 to 7.5.0 and has undergone some major changes. The `services.solr` module has been updated to reflect these changes. Please review http://lucene.apache.org/solr/ carefully before upgrading.

- Network interface indiscriminate NixOS firewall options (`networking.firewall.allow*`) are now preserved when also setting interface specific rules such as `networking.firewall.interfaces.en0.allow*`. These rules continue to use the pseudo device "default" (`networking.firewall.interfaces.default.*`), and assigning to this pseudo device will override the (`networking.firewall.allow*`) options.

- The `nscd` service now disables all caching of `passwd` and `group` databases by default. This was interferring with the correct functioning of the `libnss_systemd.so` module which is used by `systemd` to manage uids and usernames in the presence of `DynamicUser=` in systemd services. This was already the default behaviour in presence of `services.sssd.enable = true` because nscd caching would interfere with `sssd` in unpredictable ways as well. Because we're using nscd not for caching, but for convincing glibc to find NSS modules in the nix store instead of an absolute path, we have decided to disable caching globally now, as it's usually not the behaviour the user wants and can lead to surprising behaviour. Furthermore, negative caching of host lookups is also disabled now by default. This should fix the issue of dns lookups failing in the presence of an unreliable network.

- The `nscd` service now disables all caching of `passwd` and `group` databases by default. This was interfering with the correct functioning of the `libnss_systemd.so` module which is used by `systemd` to manage uids and usernames in the presence of `DynamicUser=` in systemd services. This was already the default behaviour in presence of `services.sssd.enable = true` because nscd caching would interfere with `sssd` in unpredictable ways as well. Because we're using nscd not for caching, but for convincing glibc to find NSS modules in the nix store instead of an absolute path, we have decided to disable caching globally now, as it's usually not the behaviour the user wants and can lead to surprising behaviour. Furthermore, negative caching of host lookups is also disabled now by default. This should fix the issue of dns lookups failing in the presence of an unreliable network.

  If the old behaviour is desired, this can be restored by setting the `services.nscd.config` option with the desired caching parameters.

- GitLab Shell previously used the nix store paths for the `gitlab-shell` command in its `authorized_keys` file, which might stop working after garbage collection. To circumvent that, we regenerated that file on each startup. As `gitlab-shell` has now been changed to use `/var/run/current-system/sw/bin/gitlab-shell`, this is not necessary anymore, but there might be leftover lines with a nix store path. Regenerate the `authorized_keys` file via `sudo -u git -H gitlab-rake gitlab:shell:setup` in that case.

- The `pam_unix` account module is now loaded with its control field set to `required` instead of `sufficient`, so that later PAM account modules that might do more extensive checks are being executed. Previously, the whole account module verification was exited prematurely in case a nss module provided the account name to `pam_unix`. The LDAP and SSSD NixOS modules already add their NSS modules when enabled. In case your setup breaks due to some later PAM account module previosuly shadowed, or failing NSS lookups, please file a bug. You can get back the old behaviour by manually setting `security.pam.services.<name?>.text`.

- The `pam_unix` account module is now loaded with its control field set to `required` instead of `sufficient`, so that later PAM account modules that might do more extensive checks are being executed. Previously, the whole account module verification was exited prematurely in case a nss module provided the account name to `pam_unix`. The LDAP and SSSD NixOS modules already add their NSS modules when enabled. In case your setup breaks due to some later PAM account module previously shadowed, or failing NSS lookups, please file a bug. You can get back the old behaviour by manually setting `security.pam.services.<name?>.text`.

- The `pam_unix` password module is now loaded with its control field set to `sufficient` instead of `required`, so that password managed only by later PAM password modules are being executed. Previously, for example, changing an LDAP account's password through PAM was not possible: the whole password module verification was exited prematurely by `pam_unix`, preventing `pam_ldap` to manage the password as it should.